System for detecting positional information

ABSTRACT

A mobile terminal has a simple construction in a mobile communication system of a small-zone system. The mobile terminal 1 transmits base station identification information transmitted from base stations 2a through 2d and information of the intensity of electric field of received radio wave from the base station to a position managing station, while the position managing station specifies the current position of the mobile terminal, based on the above-mentioned information by means of a relational expression of the intensity of electric field and a distance between a point of transmission and reception and a database of the base station. With the simple construction of the mobile terminal 1, the current position of the mobile terminal 1 can be specified with higher accuracy. Further, the mobile terminal 1 transmits the base station identification information of the plurality of base stations and the intensity of electric field of the received radio wave from the base station to the position managing station, the current position of the mobile terminal 1 can be specified with higher accuracy.

TECHNICAL FIELD

The present invention relates to a positional information detectingsystem for executing positional detection of a wireless mobile terminalin a mobilecommunication.

BACKGROUND ART

In recent years, mobile communication systems such as land mobile radiotelephone, portable telephone and personal handy phone system (referredto as a PHS hereinafter) have been put into practical use and arerapidly gaining popularity. For the compacting and power saving of thewireless mobile terminal (referred to as a mobile terminal hereinafter),the effective use of radio waves and the other purposes, the radio zonesof these mobile communication systems are distributed into ranges ofmicro-cells and pico-cells, which are smaller than in the conventionalcase.

In the mobile communication system, a line setting for communications isexecuted on a mobile terminal from a communication line network, therebyachieving a call. For this purpose, the registration and management ofcalling areas of the mobile terminal are executed. In theabove-mentioned systems using micro-cells and pico-cells, it is proposedto utilize a calling area registering operation of a mobile terminal forspecifying the position of the mobile terminal, taking advantage of suchfeature that each radio zone is small.

An example of the specifying of the position of a mobile terminal in thecase of the PHS will be described below.

FIG. 7 shows a construction of a PHS public service system. FIG. 8 showsa construction of a physical slot for controlling a control channel.FIG. 9 shows an operation flow at the time of registering a calling areaof a mobile terminal.

In FIG. 7, 71 denotes a mobile terminal;

72a, 72b, 72c, . . . denote base stations for executing speech callcommunications and registration of calling areas together with themobile terminal 71,

73a, 73b, 73c, . . . denote radio zones of the base stations 72a, 72b, .. . , respectively;

74 denotes a general calling area comprised of a plurality ofabove-mentioned radio zones 73a, 73b, . . . ; and

75 denotes a control station for executing control of line connection tothe mobile terminal 71 located inside the general calling area 74.

The base stations 72a, 72b, 72c, . . . are connected to one anotherthrough the control station 75 and the telecommunication line equipments76a, 76b, 76c, . . . .

The base stations 72a, 72b, 72c, . . . periodically transmit a signalincluding a general calling area number 77 of the control station 75,using a control slot shown in FIG. 8, so as to execute call connectionwith the mobile terminal 71.

FIG. 8 shows a construction of a physical slot for controlling thecontrol channel of the PHS public system, where the general calling areanumber 77 is included in an outgoing identification code section shownin the figure.

The base stations 72a, 72b, 72c, . . . managed by the control station 75transmit an identical general calling area number 77 and transmit basestation identification information that differ depending on each basestation.

The control stations of adjacent general calling areas transmitdifferent general calling area numbers. The mobile terminal 71 detectsthe change of the general calling area number and registers the callingarea in the control station via the base station.

In the operation flow of FIG. 9, the mobile terminal 71 establishes asynchronism with a signal from a base station which received a signal atthe maximum intensity of electric field in a "control channel selection"state after turning on the power, and transfers to a "waiting" statewith the recognition of "channel selection OK" when the base station canbe used. When no synchronism can be established with the base station orwhen the base station cannot be used, the control channel selection isexecuted again.

In the "waiting" state, the general calling area number transmitted fromthe currently receiving base station is compared with the generalcalling area number when the mobile terminal has executed theregistration of the calling area at the preceding time, and when thenumbers are different from each other, the calling area is registered inthe control station that controls the base station.

Further, in the "waiting" state, a difference between the retentionlevel of the intensity of electric field of waiting and the level of theintensity of received electric field is watched, thereby making adecision on radio zone transfer and zone transfer between generalcalling areas (change of registration of calling area).

If the level of the intensity of received electric field is lower thanthe retention level of the intensity of electric field for waiting, thena transfer to the "control channel selection" state is effected, and asynchronism is established with the signal from the new base stationwhich received a signal at the maximum intensity of electric field,thereby effecting a transfer to the "waiting state". In the "waitingstate", the general calling area number transmitted from the currentlyreceiving base station is compared with the general calling area numberwhen the mobile terminal has executed the registration of the callingarea at the preceding time, and when the numbers are different from eachother, the calling area is newly registered in the control station thatcontrols the base station similar to the above-mentioned case.

As described above, the mobile terminal executes the calling arearegistration, and the control station detects that the mobile terminalis located inside the calling area of the station itself.

Since the positional information (geographical information) of thecalling area that each control station manages has been already known,the current position of the mobile terminal registered in the controlstation is subordinately specified.

However, with the above-mentioned construction, the mobile terminal doesnot execute position registration until the general calling area numberchanges, and therefore, the locating or positional specifying of themobile terminal can only be executed in the unit of each general callingarea comprised of a plurality of radio zones. Therefore, theabove-mentioned construction has been insufficient for such anapplication that requires locating or positional specifying of thecurrent position of the mobile terminal with a high accuracy.

DISCLOSURE OF THE INVENTION

An object of the present invention is to solve the above-mentionedproblems, and provides a positional information detecting system capableof specifying the position of a mobile terminal with a higher accuracyin a mobile communication system of a small-zone system.

In order to achieve this object, a positional information detectingsystem of the present invention comprises:

(1) a mobile terminal;

a plurality of base stations for executing communications with themobile terminal; and

a position managing station for transmitting a signal to and receiving asignal from the mobile terminal via the base stations,

wherein the mobile terminal comprises:

an ID detection section for detecting base station identificationinformation transmitted from each of the base stations;

an intensity of electric field measuring section for measuring anintensity of electric field of received radio wave from each of the basestations; and

a transmission signal generation section for converting one or aplurality of pairs of information comprised of the base stationidentification information of one or a plurality of base stations andthe intensity of electric field of received radio wave from the basestation, into a transmission signal to the base station,

wherein the position managing station comprises:

a signal demodulation section for demodulating a signal received fromthe mobile terminal via the base station;

a database in which information of a plurality of base stations arestored; and

a position calculation section for determining the position of themobile terminal, with reference to the database, based on one or aplurality of pairs of information comprised of the base stationidentification information of one or a plurality of base stationsoutputted from the signal demodulation section and the intensity ofelectric field of the received radio wave from the base station.

(2) In addition to the above item (1), the position managing station isprovided with a mobile terminal calling section for originating a callto the mobile terminal.

(3) In the above items (1) or (2), the transmission signal generationsection converts the pair of information into a DTMF signal, and thesignal demodulation section is provided with a construction fordemodulating the received DTMF signal into the pair of information.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an arrangement view of base stations and a mobile terminalaccording to a first preferred embodiment of the present invention;

FIG. 2 is a block diagram of the mobile terminal of the above-mentionedpreferred embodiment;

FIG. 3 is a block diagram of a control station of the above-mentionedpreferred embodiment;

FIG. 4 is a plan view showing a procedure for obtaining the point of themobile terminal in the above-mentioned preferred embodiment;

FIG. 5 is a block diagram of a position managing station according to asecond preferred embodiment of the present invention;

FIG. 6 is a block diagram of a transmission data generating section ofthe mobile terminal according to a third preferred embodiment of thepresent invention;

FIG. 7 is a schematic view of a PHS public service system;

FIG. 8 is a schematic view of a physical slot of a communication controlchannel of the PHS public service; and

FIG. 9 is a chart showing an operation at the time of registering thecalling area of a mobile terminal in the case of a PHS public service.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention comprises:

a wireless mobile terminal;

a plurality of base stations for executing communications with thewireless mobile terminal; and

a position managing station for transmitting a signal to and receiving asignal from the wireless mobile terminal via the base stations,

wherein the wireless mobile terminal comprises:

an ID detection section for detecting base station identificationinformation transmitted from each of the base stations;

an intensity of electric field measuring section for measuring anintensity of electric field of received radio wave from each of the basestations; and

a transmission signal generation section for converting one or aplurality of pairs of information comprised of the base stationidentification information of one or a plurality of base stations andthe intensity of electric field of the received radio wave from the basestation, into a transmission signal to the base station,

wherein the position managing station comprises:

a signal demodulation section for demodulating a signal received fromthe wireless mobile terminal via the base station;

a database in which information of a plurality of base stations arestored; and

a position calculation section for determining a position of thewireless mobile terminal, with reference to the database, based on oneor a plurality of pairs of information comprised of the base stationidentification information of one or a plurality of base stationsoutputted from the signal demodulation section and the intensity ofelectric field of received radio wave from the base station.

With this construction, the mobile terminal detects the base stationidentification information of each base station and the information ofthe intensity of received electric field, and transmits the same to theposition managing station, and then, the position managing stationcalculates the position of the mobile terminal, with reference to thedatabase, based on a correlation between the intensity of radio wavefrom the base station and the distance from the base station to themobile terminal. Therefore, the position of the mobile terminal can bespecified with higher accuracy. Furthermore, the position managingstation can specify the position of the mobile terminal with higheraccuracy, by using the information of the intensities of radio wavesfrom the plurality of base stations transmitted from the mobileterminal.

According to the present invention, in addition to the above-mentionedinvention, the position managing station further comprises a mobileterminal calling section for originating a call to the wireless mobileterminal. With this arrangement, the mobile terminal detects the basestation identification information and the information of the intensityof electric field of the received radio wave from the base station, andthen, transmits the same to the position managing station at the timingwhen receiving the calling from the position managing station, andtherefore, the unnecessary power consumption of the mobile terminal isprevented to allow the mobile terminal to have a long battery life andcompact size. In addition, the mobile terminal can provide the updatedpositional information upon request for searching the current positionfrom the position managing station.

According to the present invention, based on the above-mentionedinvention, the transmission signal generation section converts the pairof information into a DTMF (dualtone multiple-frequency) signal, and thesignal demodulation section has a construction for demodulating thereceived DTMF signal into the pair of information. With thisarrangement, the DTMF signal generating section provided in the normalspeech communication mobile terminal can be commonly used for thegeneration of a transmission signal, so that a mobile terminal havingboth functions of speech communication and position search can beimplemented on about the same circuit scale as that of the normal speechcommunication mobile terminal.

Preferred embodiments of the present invention will be described belowwith reference to the drawings.

(First Preferred Embodiment)

A first preferred embodiment of the present invention will be, first ofall, described. FIG. 1 shows an arrangement of base stations and amobile terminal of a positional information detecting system accordingto the first preferred embodiment of the present invention. FIG. 2 showsa construction of the mobile terminal of the preferred embodiment. FIG.3 shows a construction of the position managing station of the preferredembodiment.

In FIG. 1, 1 denotes a mobile terminal;

2a, 2b, 2c, . . . denote base stations for executing communications andregistration of a calling area together with the mobile terminal 1;

3a, 3b, 3c, . . . denote radio zones of the base stations;

4 denotes a general calling area comprised of the plurality ofabove-mentioned radio zones 3a, 3b, . . . ; and

5 denotes a control station for executing control of line connection tothe mobile terminal 1 located inside the general calling area 4.

The base stations 2a, 2b, 2c, . . . are connected to one another by thecontrol station 5 and the telecommunication line equipments 6a, 6b, 6c,. . . The reference numerals 7a, 7b, 7c, . . . denote base stationidentification information that the base stations 2a, 2b, 2c, . . .periodically transmit.

In FIG. 2, 20 denotes an antenna;

21 denotes a receiving amplifier;

22 denotes a demodulation section;

23 denotes an ID detection section;

24 denotes an intensity of electric field measuring section;

25 denotes a controlling section;

26 denotes a storage section;

27 denotes a transmission signal generation section;

28 denotes a modulation section; and

29 denotes a transmitting amplifier.

In FIG. 3, 30 denotes a communication line;

32 denotes a signal demodulation section;

33 denotes a position calculation section;

34 denotes a database; and

35 denotes a display section.

An operation of the positional information detecting system constructedas discussed above will be described below.

In FIG. 1, the mobile terminal 1 is located inside the general callingarea 4 controlled by the control station 5 and executes registration ofthe calling area into the control station 5 by the operation similar tothat of the prior art. The mobile terminal 1 receives the base stationidentification information 7a, 7b, 7c, . . . that are periodicallytransmitted from the base stations 2a, 2b, 2c, . . . .

An operation of the mobile terminal 1 will be described with referenceto FIG. 2. The radio wave from each base station received by the antenna20 is amplified in the receiving amplifier 21, is converted into anintermediate frequency, and then, is demodulated into a base band signalby the demodulation section 22. The ID detection section 23 detects thebase station identification information 7a, 7b, 7c, . . . of the basestations 2a, 2b, 2c, . . . from the demodulated signal. The intensity ofelectric field measuring section 24 measures the intensity of receivedelectric field of the base stations 2a, 2b, 2c, . . . from the output ofthe receiving amplifier 21. The controlling section 25 stores into thestorage section 26, the base station identification informationoutputted from the ID detection section 23 and the information of theintensity of received electric field outputted from the intensity ofelectric field measuring section 24, as one pair of information(information pair) with regard to each base station. Each informationpair is stored into the storage section 26 with regard to the receivablebase stations inside the general calling area 4. Next, the mobileterminal 1 originates a call to the position managing station toestablish a communication state, and thereafter, the controlling section25 outputs one or a plurality of information pairs among the pluralityof stored information pairs to the transmission signal generationsection 27 sequentially from the base station having the information ofthe greater intensity of received electric field. The transmissionsignal generation section 27 converts the inputted information into asignal in a prescribed base band signal format, and then, outputs theresulting signal to the modulation section 28. The modulation section 28modulates the inputted base band signal into a high-frequency signal,and the modulated high-frequency signal is subjected to poweramplification in the transmitting amplifier 29, and then, is transmittedfrom the antenna 20 to the base stations located inside the generalcalling area 4. The signal from the mobile terminal 1 received by thebase stations is transmitted to a position managing station (not shownin FIG. 1) from the control station 5 via the communication line 30.

An operation of the position managing station will be described withreference to FIG. 3. The signal from the mobile terminal 1 received viathe communication line 30 is demodulated by the signal demodulationsection 32, and then, outputted to the position calculation section 33.The position calculation section 33 determines the position of themobile terminal 1, with reference to the database 34, based on theinputted one or a plurality of information pairs of the base stationidentification information and the intensity of received electric field.

Reference will be, first of all, made to the case where singleinformation pair of the base station identification information and theintensity of received electric field is inputted to the positioncalculation section 33.

It is known that a relation between the intensity of electric field ofthe base station at the point of reception (the position of the mobileterminal) and the distance from the base station to the point ofreception can be approximated to, for example, the following equation:

    E=A·D.sup.-α

where E represents an intensity of electric field of the base station atthe point of reception (the position of the mobile terminal), Drepresents a distance from the base station to the point of reception,and A and α are coefficients.

By using the above-mentioned equation, the distance D₁ from the mobileterminal 1 located in a position where the intensity of electric fieldof the base station is E₁ to the base station can be obtained by thefollowing equation 1, and it can be determined that the mobile terminal1 is located at a distance of the radius D₁ from the base station.

Equation 1:

    D.sub.1 =1/.sup.α √E.sub.1 /A=K·.sup.-α √E.sub.1

The database 34 stores therein the positional information (geographicalinformation of the place where the base station is located or installed)of each base station and the coefficient K of each base station. Theposition calculation section 33 obtains the distance D₁ from the basestation to the mobile terminal, with reference to the coefficient K ofthe base station from the database 34, and further specifies the pointof the mobile terminal 1 to a place in the vicinity of a circumferenceof the radius D₁ on a map, with reference to the positional informationof the base station.

Reference will be next made to the case where a plurality of informationpairs of the base station identification information and the intensityof received electric field are inputted to the position calculationsection 33, based on an example in which three information pairs of basestations 2a, 2b and 2c are inputted.

FIG. 4 is a plan view showing a procedure for obtaining the point of themobile terminal 1.

The position calculation section 33 operates in a manner similar to thatof the above-mentioned case, based on the information pair of the firstbase station 2a and determines that the mobile terminal 1 is located inthe vicinity of a circumference "a" of the radius D₁ from the position(point "a") of a base station "a" in FIG. 4. Likewise, it is determinedthat the mobile terminal 1 is located in the vicinity of a circumference"b" and a circumference "c" of radii D₂ and D₃ from the positions(points "b" and "c") of base stations "b" and "c", based on theinformation pairs of the second and third base stations 2b and 2c. Bythis operation, the position calculation section 33 specifies that themobile terminal 1 is located in the vicinity of a point d at which thecircumferences "a", "b" and "c" cross one another.

A display section 35 displays the current position of the mobileterminal 1 on the map by means of a display means such as a display.

As described above, according to the present preferred embodiment, theposition managing station is able to specify the current position of themobile terminal 1, with reference to the database 34 of the basestations, and display the point on the map, based on the informationpair of the identification information of the base stations 7a, 7b, . .. detected by the mobile terminal 1 and the intensity of receivedelectric field. The current position of the mobile terminal 1 can bespecified with higher accuracy by means of the information pairs of theplurality of base stations detected by the mobile terminal 1.

(Second Preferred Embodiment)

A second preferred embodiment of the present invention will be describednext. FIG. 5 shows a construction of a position managing station of thepresent preferred embodiment. In the present preferred embodiment, thearrangement of the base stations and the mobile terminal as well as theconstruction of the mobile terminal are the same as those of the firstpreferred embodiment shown in FIG. 1 and FIG. 2.

In FIG. 5, the reference numeral 51 denotes a mobile terminal callingsection for originating a call to the mobile terminal 1. The othercomponents are the same as those of the components of the firstpreferred embodiment shown in FIG. 3.

An operation of the positional information detecting system constructedas discussed above will be described below.

In the first preferred embodiment, the mobile terminal operates so as tooriginate a call to the position managing station and transmit theinformation pair of the base station. If it is desired to grasp thecurrent position of the mobile terminal only at a timing demanded orrequested by the position managing station, then the mobile terminal isnot always required to execute the operation of detecting andtransmitting the information pair of the base station, so that theunnecessary power consumption can be prevented. An object of the presentpreferred embodiment is to achieve this.

When the position managing station demands the information pair of thebase station from the mobile terminal 1 in order to obtain the currentposition of the mobile terminal 1, the position managing stationoriginates a call to the mobile terminal 1 by the mobile terminalcalling section 51. The mobile terminal 1 receives a calling signal ofthe position managing station from the base station inside the generalcalling area 4 via a communication line 30 and the control station 5.The mobile terminal 1 executes the same operation as described inconnection with the first preferred embodiment immediately afterreception, and transmits one or a plurality of information pairs of thebase station identification information and the intensity of receivedelectric field to the position managing station. The operation differentfrom that of the first preferred embodiment resides in such a point thatthe mobile terminal 1 transmits the information to the position managingstation according to the reception from the position managing stationand originate no call to the position managing station. The mobileterminal 1 is, of course, allowed to once disconnect the speechcommunication after the reception from the position managing station,and then execute again completely the same operation as that of thefirst preferred embodiment. Therefore, when no call is received from theposition managing station, the mobile terminal 1 is not required toexecute the operation of detecting and transmitting the information pairof the base station, so that the power consumption can be reduced.

The position managing station executes completely the same operation asthat of the first preferred embodiment, thereby displaying the currentposition of the mobile terminal 1 on the map after receiving theinformation pair of the base station from the mobile terminal 1.

As described above, according to the present preferred embodiment, themobile terminal 1 detects the information pair of the base station onlywhen the position managing station originates a call to the mobileterminal 1 and transmits the information pair to the position managingstation, thereby allowing the power consumption of the mobile terminal 1to be reduced in addition to the effect described in connection with thefirst preferred embodiment. The mobile terminal 1 can provide theupdated positional information upon request for searching the currentposition from the position managing station.

(Third Preferred Embodiment)

A third preferred embodiment of the present invention will be describednext. FIG. 6 shows a construction of a transmission data generatingsection of a mobile terminal according to the third preferredembodiment. In FIG. 6,

61 denotes a transmission signal generating section;

62 denotes a DTMF signal generation section provided in the front stageinside the transmission signal generating section 61;

63 denotes a data slot generation section provided in the rear stageinside the transmission signal generating section 61.

The other components of the mobile terminal are the same as those of thecomponents of the first preferred embodiment shown in FIG. 2. Thearrangement of the base stations and the mobile terminal as well as theconstruction of the position managing station are the same as those ofthe first preferred embodiment shown in FIGS. 1 and 3.

An operation of the present preferred embodiment constructed asdiscussed above will be described below. The audio processing section ofthe normal mobile terminal for speech communication use is provided witha DTMF signal generation section for generating an audio signalcorresponding to each dial key. An object of the present preferredembodiment is to enable completely the same function of specifying theposition of the mobile terminal as that of the first preferredembodiment by changing the software of the control section withoutincorporating any separate voice modem into the normal mobile terminalfor speech communication use by converting the one or a plurality ofbase station identification information and the information of theintensity of received electric field as stated in connection with thefirst preferred embodiment into a DTMF signal and thereafter convertingthe resulting signal into a signal having a specified base band signalformat.

The operations up to the operation of the controlling section 25 foroutputting the one or a plurality of base station identificationinformation and the information of the intensity of received electricfield are completely the same as those described in connection with thefirst preferred embodiment. The DTMF signal generation section 62converts the inputted information into a DTMF speech signal, and thedata slot generation section 63 outputs the inputted DIMF speech signalinto a signal having a specified base band digital data slot format, andoutputs the resulting signal to the modulation section 28. Thesubsequent operations are completely the same as the operationsdescribed in connection with the first preferred embodiment. Theposition managing station demodulates the DTMF signal received from themobile terminal 1 into one or a plurality of base station identificationinformation and the information of the intensity of received electricfield by the signal demodulation section 32, and subsequently displaysthe current position of the mobile terminal 1 on the map throughcompletely the same operation as that of the first preferred embodiment.

As described above, according to the present preferred embodiment, byapplying the DTMF speech signal to the generation of the transmissionsignal of the mobile terminal 1, the DTMF signal generation sectionprovided in the normal mobile terminal for speech communication use canbe commonly used, so that a mobile terminal provided with both thespeech communication function and completely the same positionspecifying function as that described in connection with the firstpreferred embodiment can be implemented on a circuit scale equivalent tothat of the normal mobile terminal for speech communication use.

It is, of course, acceptable to apply the construction of the presentpreferred embodiment to the second preferred embodiment.

Industrial Applicability

As described above, the present invention can produce the effects asfollows.

(1) The mobile terminal transmits the base station identificationinformation transmitted from the base station and the information of theintensity of electric field of the radio wave received by the basestation to the position managing station, and the position managingstation can specify the current position of the mobile terminal withhigher accuracy, with reference to the database of the base stations,based on the above-mentioned information. Furthermore, the mobileterminal transmits the base station identification information of aplurality of base stations and the information of the intensity ofelectric field of the radio wave received by the base stations to theposition managing station, thereby allowing the current position of themobile terminal to be specified with higher accuracy.

(2) The position managing station originates a call to the mobileterminal at a timing when the current position of the mobile terminal isdesired to be grasped, and

the mobile terminal detects the base station identification informationand the information of the intensity of electric field of the radio wavereceived by the base station only when a call occurs from the positionmanaging station and transmits the information to the position managingstation so that the unnecessary power consumption of the mobile terminalis prevented to allow the mobile terminal to have a long battery lifeand compact size. In addition, the position managing station can graspthe updated current position of the mobile terminal.

(3) By applying the DTMF speech signal to the generation of thetransmission signal of the mobile terminal, the DTMF signal generationsection provided in the normal mobile terminal for communication use canbe commonly used, so that a mobile terminal provided with both thespeech communication function and the position specifying function canbe implemented on the circuit scale equivalent to that of the normalmobile terminal for speech communication use.

What is claimed is:
 1. A positional information detecting systemcomprising:a wireless mobile terminal; a plurality of base stations forexecuting communications with said wireless mobile terminal; and aposition managing station for executing communications with saidwireless mobile terminal via said base stations, wherein said wirelessmobile terminal comprises:an ID detection section for detecting basestation identification information transmitted from each of said basestations; an intensity of electric field measuring section for measuringan intensity of electric field of received radio wave from each of saidbase stations; and a transmission signal generation section forconverting one pair or a plurality of pairs of information comprised ofthe base station identification information of one or a plurality ofbase stations and the intensity of electric field of received radio wavefrom said base station, into a transmission signal to said base station,wherein said position managing station comprises:a signal demodulationsection for demodulating a signal received from said wireless mobileterminal via said base station; a database for storing thereingeographical information of a place where each base station of aplurality of base stations is located and a base station coefficient ofeach base station; and a position calculation section for determining aposition of said wireless mobile terminal, with reference to saiddatabase, based on one pair or a plurality of pairs of informationcomprised of the base station identification information of one or aplurality of base stations outputted from said signal demodulationsection and the intensity of electric field of received radio wave fromsaid base station, wherein said position calculation section calculatesa distance of a radius from said base station to said wireless mobileterminal, based on the intensity of electric field of the received radiowave from said base station and a base station coefficient of said basestation stored in said database, by means of an approximate equation forcalculating the distance of the radius from said base station to saidwireless mobile terminal according to the intensity of electric field ofthe received radio wave from said base station and the base stationcoefficient, and then, determines the position of said wireless mobileterminal, based on the calculated distance of the radius and thegeographical information of the places of said base stations stored insaid database.
 2. The positional information detecting system as claimedin claim 1,wherein said position managing station further comprises amobile terminal calling section for originating a call to said wirelessmobile terminal.
 3. The positional information detecting system asclaimed in claim 2,wherein said transmission signal generation sectionconverts one pair of information into a DTMF signal as said transmissionsignal, and said signal demodulation section demodulates the receivedDTMF signal into said one pair of information.
 4. The positionalinformation detecting system as claimed in claim 1,wherein saidtransmission signal generation section converts one pair of informationinto a DTMF signal as said transmission signal, and said signaldemodulation section demodulates the received DTMF signal into said onepair of information.